1. Field of the Invention
The present invention relates to a magnetic recording medium used for an information recording/reproducing device, such as a hard disk device.
2. Description of the Related Art
In recent years, moves towards the downsizing and increasing in capacity of magnetic recording/reproducing devices are rapidly progressing. In order to increase the magnetic recording density of the magnetic recording medium used for a magnetic recording/reproducing device, it is essential to decrease the noises of the magnetic recording medium, and for this purpose, it is necessary to decrease and make uniform the particle size of a hard magnetic substance used for the magnetic recording layer. In addition, in the case of a disk-shaped magnetic recording medium, the magnetic recording density is determined by the magnetic recording track density in the radial direction and the density in the circumferential direction which is called the “line recording density”. Accordingly, in order to improve the magnetic recording density of the magnetic recording medium, it is also important to increase the magnetic recording track density in the radial direction. As a method for increasing the magnetic recording track density in the radial direction, a magnetic recording medium called “discrete track medium” has been proposed and researched/developed. This is a magnetic recording medium having a structure to make magnetic recording tracks narrower by separating adjacent magnetic recording tracks {see Japanese Unexamined Patent Application Publication No. H4-310621 (Claims)}.
As a means for separating the magnetic recording tracks of a magnetic recording layer as described above, a structure for separating the magnetic recording layer structurally by a non-magnetic material, and a structure for separating the magnetic recording tracks magnetically by separating the soft magnetic material of the backing layer (or soft magnetic layer), are proposed. In the latter case, the soft magnetic layer is structurally separated, so the magnetic recording layer has a structure which forms a continuous layer without separation.
A feature in common in both means is that protrusions/recesses for the purpose of separation are created on the non-magnetic material or on the surface of the substrate under the backing layer. Therefore a final step of flattening the magnetic recording layer surface is always required so that the magnetic head smoothly flies and moves over the layer.
In a type wherein the magnetic recording layer is separated by a non-magnetic material, for example, protrusions/recesses are created by a resist pattern or the like after an intermediate layer is formed, for example, then steps of stripping the resist, forming a non-magnetic material film, forming a magnetic recording layer film by a sputtering method or the like, polishing for surface smoothing, etc. are required.
In the structure wherein the backing layer is separated, on the other hand, protrusions/recesses are created on the substrate by a resist pattern, for example, then steps of forming a backing layer film, stripping the resist, forming a non-magnetic material film, surface smoothing, polishing and forming a magnetic recording layer film by a sputtering method or the like are required.
In other words, in both cases a polishing step or other steps are required. Details on the fabrication methods may be different from the example shown here, but such a situation is the same for the two methods.
The flying height of a magnetic head, however, is about 10 nm, and it is very difficult to accomplish the surface smoothness of the magnetic recording layer (surface of the sputtered film) required for this flying height. Even if it is accomplished, a very large number of processing steps and manufacturing facilities are required, resulting in a serious problem in terms of cost.
It is an object of the present invention to solve the above-described problems, and provide a new discrete track medium which has a high magnetic recording density, and a manufacturing method therefor. Other objects and advantages of the present invention shall be clarified by the following description.